Diverse Bacteriophages Infecting the Bacterial Striped Catfish Pathogen Edwardsiella ictaluri.

Le T. My Duyen,Pham D. T. My,Hoang A. Hoang,Tan-Trung Nguyen,Le P. Nga,Tran T. T. Xuan,To H. Ngoc,Tu Q. Vinh

doi:10.3390/microorganisms9091830

Le T. My Duyen, Pham D. T. My + Show 6 more

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https://doi.org/10.3390/microorganisms9091830

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Abstract

Bacteriophages infecting Edwardsiella ictaluri have been less investigated, although the host bacterium is one of the most important fish pathogens causing enteric septicemia of catfish (ESC). We present here two distinctly novel bacteriophages vB_EiM_PVN06 and vB_EiA_PVN09 infecting Edwardsiella ictaluri E1, with their geographical origins from the Mekong Delta, Vietnam. Bacteriophage vB_EiM_PVN06 native to a mud sample reveals complete differences of biological properties with the phage vB_EiA_PVN09 originated from a viscus of a healthy catfish (Pangasianodon hypophthalmus) cultured in the same area. Morphological analyses combined with genomic data indicate that phage vB_EiM_PVN06 is classified to Myoviridae family and shares high similarity with E. ictaluri phage PEi21 genome, while vB_EiA_PVN09 is a member of Teseptimavirus genus, Autographiviridae family, and mostly closes to phage vB_EcoP_IME390. The vB_EiA_PVN09 is a T7-like bacteriophage, which has been firstly found infecting to E. ictaluri, and host range analysis also evidences for the cross-infection of this phage to Escherichia coli K12 and Escherichia coli DH5α. Together, our research highlights the diversity of bacteriophages infecting the pathogen E. ictaluri and suggests further explorations of lytic phages in environmental niches, to be exploited in feasible strategies of phage therapy in ESC disease control.

Highlights

Enteric septicemia of catfish (ESC) with typical symptoms including white spots in the internal organs such as the liver, kidney, and spleen, caused by the primary fish bacterial pathogens Edwardsiella ictaluri and Edwardsiella tarda, was recognized as a highly infectious disease of catfish families in different geographical locations inNorth America and Asia [1,2,3,4,5]
As a strategy to identify novel phages that could be harnessed in phage therapy to control the pathogen in Mekong Delta, Vietnam, we isolated successfully two novel E. ictaluri phages (including vB_EiM_PVN06 (PVN06) and vB_EiA_PVN09 (PVN09)) from the mud sample and the homogenized internal organ of healthy fish, respectively
According to morphology and genome analysis of the phage PVN09, we firstly identified a T7-like phage classified to Teseptimavirus genus with diverse members, in Autographiviridae family, which was against the host

Summary

Introduction

Enteric septicemia of catfish (ESC) with typical symptoms including white spots in the internal organs such as the liver, kidney, and spleen, caused by the primary fish bacterial pathogens Edwardsiella ictaluri and Edwardsiella tarda, was recognized as a highly infectious disease of catfish families in different geographical locations inNorth America and Asia [1,2,3,4,5]. To treat and control the primary causative agent E. ictaluri in fish farms, abuse of antibiotics was highly prevalent; it caused negative impacts to the environment, antibiotic resistance, and over-accumulated antibiotic residues in frozen catfish products [7,8,9]. Due to the fascinating biological properties of phages, they were ideally considered to be employed as natural bio-control agents in alternative methods to fight against the pathogenic bacteria [12,13]. To understand the diversity of phages infecting the enteric Gram-negative fish pathogen E. ictaluri and to identify lytic phages that could be exploited in effective bio-control strategies of the pathogen, we aimed to isolate, characterize, and sequence novel lytic E. ictaluri phages from different sources

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